1. Field of the Invention
The present invention relates to an image forming apparatus. More particularly, the present invention relates to an image forming apparatus equipped with a pick-up roller to pick up a sheet.
2. Description of the Prior Art
Generally, an image forming apparatus prints an image on print media (e.g., a sheet) by using an input image signal. Such an image forming apparatus irradiates a laser beam onto a photo-conductive drum charged with predetermined potential to form an electrostatic latent image on the outer peripheral surface thereof, applies a developer to the electrostatic latent image to make a visible image, transfers and fixes the visible image onto a sheet, thus printing the visible image on the sheet.
As disclosed in Korean Unexamined Publication No. 10-2005-110224, conventional image forming apparatuses include a body forming an outer appearance of the image forming apparatus, a sheet feeding unit to supply a sheet which is a printing medium, an image forming unit to form an image on the sheet, a fixing unit to fix the image onto the sheet by applying heat and pressure onto the sheet, and a sheet discharging unit to discharge the sheet having undergone the printing operation to the outside of the body.
In the above image forming apparatuses, there is an image forming apparatus including a sheet feeding unit equipped with a sheet feeding tray having sheets stacked thereon, a pick-up roller to pick up one of the sheets stacked on the sheet feeding tray, a pair of regi-rollers to arrange the sheets, and a regi-shutter, which is rotatably mounted on one of the regi-rollers, and which rotates only when a sheet feeding pressure exceeding a predetermined value is applied to allow the sheet to enter the space between the two regi-rollers.
Since the pick-up roller may simultaneously pick up a plurality of sheets when the sheet feeding pressure exceeds the predetermined value, the sheet feeding pressure must be limited to below certain level. However, the regi-shutter rotates only when the sheet feeding pressure exceeding the predetermined value is exerted on a sheet to enable the sheet to pass through the space between the regi-rollers.
The conventional image forming apparatus further requires a feed roller between the pick-up roller and the regi-roller to generate a sheet feeding pressure exceeding a predetermined value, and to deliver the sheet feeding pressure to the sheet, such that the sheet can enter the space between the regi-rollers while rotating the regi-shutter.
As described above, in the conventional image forming apparatus, since the feed roller must be installed between the pick-up roller and the regi-roller, not only the structure of the conventional image forming apparatus may become complicated, but also the height thereof may be increased in order to ensure the installation space of the feed roller.